Morphology and morphometry of the rat lacrimal gland duct system: a comparative analysis of the extraorbital, intraorbital, and Harderian glands

In our studies, we assumed that the lacrimal gland of the laboratory rat, like its human counterparts, is a polymeric organ that has its own specifics. This primarily concerns the syntopic relationships in the three-dimensional space of the glands themselves and their microstructures. Therefore, when studying the lacrimal glands of the rat (extraorbital, infraorbital and Garder's), as well as when studying human glands, we needed to identify the level of structural organization of diverse tissues that would correspond to the concept of a structural-functional unit. The purpose of the study: to characterize morphometrically and histologically the terminal departments and the system of excretory ducts of the extraorbital, intraorbital and Garder's lacrimal glands of the rat and to determine their general biological and species-specific features. A morphometric and histological analysis of the extraorbital, intraorbital and Garder's lacrimal glands of the laboratory rat was carried out. The results obtained were processed in Microsoft Excel. It was found that the terminal sections have a larger outer diameter and wall thickness compared to the interstitial ducts. The intralobular ducts are characterized by larger luminal lumens, which contributes to the effective accumulation and evacuation of secretion. In the Garder gland, the terminal sections often have an irregular shape and narrow lumens, and the interstitial ducts are almost identical in diameter to the terminal ones. Myoepithelial cells participate in the reduction and modulation of secretion, creating a “milking” effect that ensures secretion. Comparison of the obtained data with the morphometry of the human lacrimal gland allows us to identify general biological patterns of the organization of the excretory system and species-specific adaptations to the type of secretion and functional needs. The results of the study are important for a deeper understanding of the morphofunctional organization of the lacrimal glands and can serve as a basis for further physiological and pathological studies of exocrine glands.